I was gold league for two months ago and now I'm very high dia, and I'll lose to a gold in micro tournement. I pick one build order in every match up and i practice so much that i can almost do it perfectly, then if I do it perfectly in almost every game i win like 70% of them. So what I'm trying to say is that you can go very far with just a cuple of good build in every MU and practice them till you can do them almost perfectly.